Method and apparatus for video coding

ABSTRACT

Aspects of the disclosure provide methods and apparatuses for video encoding/decoding. Processing circuitry decodes prediction information of a block from a coded video bitstream. The prediction information is indicative of a matrix based intra prediction for the block. The processing circuitry determines entries of a vector based on neighboring samples of the block. An entry can be determined based on one or more neighboring samples of the block. The processing circuitry converts the entries into a reduced bit form with a number of bits satisfying a requirement of using a first multiplication tool that processes fewer bits than a second multiplication tool. Then, the processing circuitry multiplies, using the first multiplication tool, the entries of the vector in the reduced bit form with entries of a matrix to calculate a subset of prediction samples of the block, and determines other prediction samples of the block based on the subset.

INCORPORATION BY REFERENCE

This application is a Continuation of U.S. patent application Ser. No.16/940,874, filed Jul. 28, 2020, which claims the benefit of priority toU.S. Provisional Application No. 62/886,307, “IMPROVED MATRIX BASEDINTRA PREDICTION” filed on Aug. 13, 2019 and U.S. ProvisionalApplication No. 62/910,119, “MATRIX BASED INTRA PREDICTION” filed onOct. 3, 2019, wherein the entire content and disclosures of each ofwhich are incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Video coding and decoding can be performed using inter-pictureprediction with motion compensation. Uncompressed digital video caninclude a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has specific bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GBytes of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reduce the aforementioned bandwidth and/or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless compression and lossy compression, as well as a combinationthereof can be employed. Lossless compression refers to techniques wherean exact copy of the original signal can be reconstructed from thecompressed original signal. When using lossy compression, thereconstructed signal may not be identical to the original signal, butthe distortion between original and reconstructed signals is smallenough to make the reconstructed signal useful for the intendedapplication. In the case of video, lossy compression is widely employed.The amount of distortion tolerated depends on the application; forexample, users of certain consumer streaming applications may toleratehigher distortion than users of television distribution applications.The compression ratio achievable can reflect that: higherallowable/tolerable distortion can yield higher compression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding.

Video codec technologies can include techniques known as intra coding.In intra coding, sample values are represented without reference tosamples or other data from previously reconstructed reference pictures.In some video codecs, the picture is spatially subdivided into blocks ofsamples. When all blocks of samples are coded in intra mode, thatpicture can be an intra picture. Intra pictures and their derivationssuch as independent decoder refresh pictures, can be used to reset thedecoder state and can, therefore, be used as the first picture in acoded video bitstream and a video session, or as a still image. Thesamples of an intra block can be exposed to a transform, and thetransform coefficients can be quantized before entropy coding. Intraprediction can be a technique that minimizes sample values in thepre-transform domain. In some cases, the smaller the DC value after atransform is, and the smaller the AC coefficients are, the fewer thebits that are required at a given quantization step size to representthe block after entropy coding.

Traditional intra coding such as known from, for example MPEG-2generation coding technologies, does not use intra prediction. However,some newer video compression technologies include techniques thatattempt, from, for example, surrounding sample data and/or metadataobtained during the encoding/decoding of spatially neighboring, andpreceding in decoding order, blocks of data. Such techniques arehenceforth called “intra prediction” techniques. Note that in at leastsome cases, intra prediction is using reference data only from thecurrent picture under reconstruction and not from reference pictures.

There can be many different forms of intra prediction. When more thanone of such techniques can be used in a given video coding technology,the technique in use can be coded in an intra prediction mode. Incertain cases, modes can have submodes and/or parameters, and those canbe coded individually or included in the mode codeword. Which codewordto use for a given mode/submode/parameter combination can have an impactin the coding efficiency gain through intra prediction, and so can theentropy coding technology used to translate the codewords into abitstream.

A certain mode of intra prediction was introduced with H.264, refined inH.265, and further refined in newer coding technologies such as jointexploration model (JEM), versatile video coding (VVC), and benchmark set(BMS). A predictor block can be formed using neighboring sample valuesbelonging to already available samples. Sample values of neighboringsamples are copied into the predictor block according to a direction. Areference to the direction in use can be coded in the bitstream or mayitself be predicted.

Referring to FIG. 1, depicted in the lower right is a subset of ninepredictor directions known from H.265's 33 possible predictor directions(corresponding to the 33 angular modes of the 35 intra modes). The pointwhere the arrows converge (101) represents the sample being predicted.The arrows represent the direction from which the sample is beingpredicted. For example, arrow (102) indicates that sample (101) ispredicted from a sample or samples to the upper right, at a 45 degreeangle from the horizontal. Similarly, arrow (103) indicates that sample(101) is predicted from a sample or samples to the lower left of sample(101), in a 22.5 degree angle from the horizontal.

Still referring to FIG. 1, on the top left there is depicted a squareblock (104) of 4×4 samples (indicated by a dashed, boldface line). Thesquare block (104) includes 16 samples, each labelled with an “S”, itsposition in the Y dimension (e.g., row index) and its position in the Xdimension (e.g., column index). For example, sample S21 is the secondsample in the Y dimension (from the top) and the first (from the left)sample in the X dimension. Similarly, sample S44 is the fourth sample inblock (104) in both the Y and X dimensions. As the block is 4×4 samplesin size, S44 is at the bottom right. Further shown are reference samplesthat follow a similar numbering scheme. A reference sample is labelledwith an R, its Y position (e.g., row index) and X position (columnindex) relative to block (104). In both H.264 and H.265, predictionsamples neighbor the block under reconstruction; therefore no negativevalues need to be used.

Intra picture prediction can work by copying reference sample valuesfrom the neighboring samples as appropriated by the signaled predictiondirection. For example, assume the coded video bitstream includessignaling that, for this block, indicates a prediction directionconsistent with arrow (102)—that is, samples are predicted from aprediction sample or samples to the upper right, at a 45 degree anglefrom the horizontal. In that case, samples S41, S32, S23, and S14 arepredicted from the same reference sample R05. Sample S44 is thenpredicted from reference sample R08.

In certain cases, the values of multiple reference samples may becombined, for example through interpolation, in order to calculate areference sample; especially when the directions are not evenlydivisible by 45 degrees.

The number of possible directions has increased as video codingtechnology has developed. In H.264 (year 2003), nine different directioncould be represented. That increased to 33 in H.265 (year 2013), andJEM/VVC/BMS, at the time of disclosure, can support up to 65 directions.Experiments have been conducted to identify the most likely directions,and certain techniques in the entropy coding are used to represent thoselikely directions in a small number of bits, accepting a certain penaltyfor less likely directions. Further, the directions themselves cansometimes be predicted from neighboring directions used in neighboring,already decoded, blocks.

FIG. 2 shows a schematic (201) that depicts 65 intra predictiondirections according to JEM to illustrate the increasing number ofprediction directions over time.

The mapping of intra prediction directions bits in the coded videobitstream that represent the direction can be different from videocoding technology to video coding technology; and can range, forexample, from simple direct mappings of prediction direction to intraprediction mode, to codewords, to complex adaptive schemes involvingmost probable modes, and similar techniques. In all cases, however,there can be certain directions that are statistically less likely tooccur in video content than certain other directions. As the goal ofvideo compression is the reduction of redundancy, those less likelydirections will, in a well working video coding technology, berepresented by a larger number of bits than more likely directions.

SUMMARY

Aspects of the disclosure provide methods and apparatuses for videoencoding/decoding. In some examples, an apparatus for video decodingincludes receiving circuitry and processing circuitry. The processingcircuitry decodes prediction information of a block from a coded videobitstream. The prediction information is indicative of a matrix basedintra prediction for the block. Then, the processing circuitrydetermines entries of a vector based on neighboring samples of theblock. In an example, each entry is determined based on one or moreneighboring samples of the block. The processing circuitry converts theentries of the vector into a reduced bit form with a number of bitssatisfying a requirement of using a first multiplication tool thatprocesses fewer bits than a second multiplication tool. Then, theprocessing circuitry multiplies, using the first multiplication tool,the entries of the vector in the reduced bit form with entries of amatrix to calculate a subset of prediction samples of the block, anddetermines other prediction samples of the block based on the subset ofthe prediction samples of the block.

In some embodiments, the processing circuitry performs at least one ofright shifting an entry by one or more bits and clipping the entry to arange corresponding to fewer bits.

In an embodiment, the processing circuitry right shifts the entries ofthe vector by a number of bits and modifies, based on the number ofbits, a weight shifting variable that is used for aligningmultiplication results.

In some embodiments, the processing circuitry uses a filtering tool todetermine the entries of the vector based on the neighboring samples ofthe block, the filtering tool being used in a non-matrix based intraprediction. In some embodiments, the processing circuitry selects asubset of the neighboring samples of the block as the entries of thevector based on positions of the neighboring samples with reference tothe block. In an embodiment, the processing circuitry filters firstneighboring samples on a first side of the block to determine a firstportion of the entries of the vector, and selects a second portion ofthe entries of the vector from second neighboring samples on a secondside of the block.

In an embodiment, the processing circuitry sets one or more otherprediction samples between two prediction samples in the subset to be anaverage of the two samples.

In some examples, the processing circuitry modifies a factor parameterto have a power of two value. The factor parameter is used to unify theentries of the matrix to have a same sign.

In some embodiments, the number of bits to shift is determined based onat least one of an internal bit depth, a signal in a high level syntax,and a look-up table. In an example, the processing circuitry decodes alookup table from a high level syntax. The lookup table associatesshifting bits with internal bit depths. The processing circuitrydetermines the number of bits from the lookup table.

Aspects of the disclosure also provide a non-transitorycomputer-readable medium storing instructions which when executed by acomputer for video decoding cause the computer to perform the method forvideo decoding.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of an exemplary subset of intraprediction modes.

FIG. 2 is an illustration of exemplary intra prediction directions.

FIG. 3 is a schematic illustration of a simplified block diagram of acommunication system (300) in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of acommunication system (400) in accordance with an embodiment.

FIG. 5 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 6 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 7 shows a block diagram of an encoder in accordance with anotherembodiment.

FIG. 8 shows a block diagram of a decoder in accordance with anotherembodiment.

FIG. 9 shows an illustration of intra prediction directions and theintra prediction modes in some examples.

FIG. 10 shows another illustration of intra prediction directions andintra prediction modes in some examples.

FIG. 11 shows a diagram illustrating a first step of matrix based intraprediction in some examples.

FIG. 12 shows a diagram illustrating a second step of matrix based intraprediction in some examples.

FIG. 13 shows a diagram illustrating a third step of matrix based intraprediction in some examples.

FIG. 14 shows a diagram of a current block having a size of 8×8 andneighboring samples.

FIG. 15 shows a diagram of a current block having a size of 16×16 andneighboring samples.

FIG. 16 shows a flow chart outlining a process example according to anembodiment of the disclosure.

FIG. 17 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 3 illustrates a simplified block diagram of a communication system(300) according to an embodiment of the present disclosure. Thecommunication system (300) includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network (350). Forexample, the communication system (300) includes a first pair ofterminal devices (310) and (320) interconnected via the network (350).In the FIG. 3 example, the first pair of terminal devices (310) and(320) performs unidirectional transmission of data. For example, theterminal device (310) may code video data (e.g., a stream of videopictures that are captured by the terminal device (310)) fortransmission to the other terminal device (320) via the network (350).The encoded video data can be transmitted in the form of one or morecoded video bitstreams. The terminal device (320) may receive the codedvideo data from the network (350), decode the coded video data torecover the video pictures and display video pictures according to therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

In another example, the communication system (300) includes a secondpair of terminal devices (330) and (340) that performs bidirectionaltransmission of coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices (330) and (340)may code video data (e.g., a stream of video pictures that are capturedby the terminal device) for transmission to the other terminal device ofthe terminal devices (330) and (340) via the network (350). Eachterminal device of the terminal devices (330) and (340) also may receivethe coded video data transmitted by the other terminal device of theterminal devices (330) and (340), and may decode the coded video data torecover the video pictures and may display video pictures at anaccessible display device according to the recovered video data.

In the FIG. 3 example, the terminal devices (310), (320), (330) and(340) may be illustrated as servers, personal computers and smart phonesbut the principles of the present disclosure may be not so limited.Embodiments of the present disclosure find application with laptopcomputers, tablet computers, media players and/or dedicated videoconferencing equipment. The network (350) represents any number ofnetworks that convey coded video data among the terminal devices (310),(320), (330) and (340), including for example wireline (wired) and/orwireless communication networks. The communication network (350) mayexchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(350) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 4 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (413), that caninclude a video source (401), for example a digital camera, creating forexample a stream of video pictures (402) that are uncompressed. In anexample, the stream of video pictures (402) includes samples that aretaken by the digital camera. The stream of video pictures (402),depicted as a bold line to emphasize a high data volume when compared toencoded video data (404) (or coded video bitstreams), can be processedby an electronic device (420) that includes a video encoder (403)coupled to the video source (401). The video encoder (403) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video data (404) (or encoded video bitstream (404)),depicted as a thin line to emphasize the lower data volume when comparedto the stream of video pictures (402), can be stored on a streamingserver (405) for future use. One or more streaming client subsystems,such as client subsystems (406) and (408) in FIG. 4 can access thestreaming server (405) to retrieve copies (407) and (409) of the encodedvideo data (404). A client subsystem (406) can include a video decoder(410), for example, in an electronic device (430). The video decoder(410) decodes the incoming copy (407) of the encoded video data andcreates an outgoing stream of video pictures (411) that can be renderedon a display (412) (e.g., display screen) or other rendering device (notdepicted). In some streaming systems, the encoded video data (404),(407), and (409) (e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Coding(VVC). The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (420) and (430) can includeother components (not shown). For example, the electronic device (420)can include a video decoder (not shown) and the electronic device (430)can include a video encoder (not shown) as well.

FIG. 5 shows a block diagram of a video decoder (510) according to anembodiment of the present disclosure. The video decoder (510) can beincluded in an electronic device (530). The electronic device (530) caninclude a receiver (531) (e.g., receiving circuitry). The video decoder(510) can be used in the place of the video decoder (410) in the FIG. 4example.

The receiver (531) may receive one or more coded video sequences to bedecoded by the video decoder (510); in the same or another embodiment,one coded video sequence at a time, where the decoding of each codedvideo sequence is independent from other coded video sequences. Thecoded video sequence may be received from a channel (501), which may bea hardware/software link to a storage device which stores the encodedvideo data. The receiver (531) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (531) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (515) may be coupled inbetween the receiver (531) and an entropy decoder/parser (520) (“parser(520)” henceforth). In certain applications, the buffer memory (515) ispart of the video decoder (510). In others, it can be outside of thevideo decoder (510) (not depicted). In still others, there can be abuffer memory (not depicted) outside of the video decoder (510), forexample to combat network jitter, and in addition another buffer memory(515) inside the video decoder (510), for example to handle playouttiming. When the receiver (531) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosynchronous network, the buffer memory (515) may not be needed, orcan be small. For use on best effort packet networks such as theInternet, the buffer memory (515) may be required, can be comparativelylarge and can be advantageously of adaptive size, and may at leastpartially be implemented in an operating system or similar elements (notdepicted) outside of the video decoder (510).

The video decoder (510) may include the parser (520) to reconstructsymbols (521) from the coded video sequence. Categories of those symbolsinclude information used to manage operation of the video decoder (510),and potentially information to control a rendering device such as arender device (512) (e.g., a display screen) that is not an integralpart of the electronic device (530) but can be coupled to the electronicdevice (530), as was shown in FIG. 5. The control information for therendering device(s) may be in the form of Supplemental EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (520) mayparse/entropy-decode the coded video sequence that is received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow various principles,including variable length coding, Huffman coding, arithmetic coding withor without context sensitivity, and so forth. The parser (520) mayextract from the coded video sequence, a set of subgroup parameters forat least one of the subgroups of pixels in the video decoder, based uponat least one parameter corresponding to the group. Subgroups can includeGroups of Pictures (GOPs), pictures, tiles, slices, macroblocks, CodingUnits (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) andso forth. The parser (520) may also extract from the coded videosequence information such as transform coefficients, quantizer parametervalues, motion vectors, and so forth.

The parser (520) may perform an entropy decoding/parsing operation onthe video sequence received from the buffer memory (515), so as tocreate symbols (521).

Reconstruction of the symbols (521) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (520). The flow of such subgroup control information between theparser (520) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (510)can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (551). Thescaler/inverse transform unit (551) receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (521) from the parser (520). The scaler/inversetransform unit (551) can output blocks comprising sample values, thatcan be input into aggregator (555).

In some cases, the output samples of the scaler/inverse transform (551)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (552). In some cases, the intra pictureprediction unit (552) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current picture buffer (558). The currentpicture buffer (558) buffers, for example, partly reconstructed currentpicture and/or fully reconstructed current picture. The aggregator(555), in some cases, adds, on a per sample basis, the predictioninformation the intra prediction unit (552) has generated to the outputsample information as provided by the scaler/inverse transform unit(551).

In other cases, the output samples of the scaler/inverse transform unit(551) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (553) canaccess reference picture memory (557) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (521) pertaining to the block, these samples can beadded by the aggregator (555) to the output of the scaler/inversetransform unit (551) (in this case called the residual samples orresidual signal) so as to generate output sample information. Theaddresses within the reference picture memory (557) from where themotion compensation prediction unit (553) fetches prediction samples canbe controlled by motion vectors, available to the motion compensationprediction unit (553) in the form of symbols (521) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory (557) when sub-sample exact motion vectors are in use,motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (555) can be subject to variousloop filtering techniques in the loop filter unit (556). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video sequence (alsoreferred to as coded video bitstream) and made available to the loopfilter unit (556) as symbols (521) from the parser (520), but can alsobe responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit (556) can be a sample stream that canbe output to the render device (512) as well as stored in the referencepicture memory (557) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser (520)), the current picture buffer (558) can becomea part of the reference picture memory (557), and a fresh currentpicture buffer can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder (510) may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as documented in thevideo compression technology or standard. Specifically, a profile canselect certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver (531) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (510) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 6 shows a block diagram of a video encoder (603) according to anembodiment of the present disclosure. The video encoder (603) isincluded in an electronic device (620). The electronic device (620)includes a transmitter (640) (e.g., transmitting circuitry). The videoencoder (603) can be used in the place of the video encoder (403) in theFIG. 4 example.

The video encoder (603) may receive video samples from a video source(601) (that is not part of the electronic device (620) in the FIG. 6example) that may capture video image(s) to be coded by the videoencoder (603). In another example, the video source (601) is a part ofthe electronic device (620).

The video source (601) may provide the source video sequence to be codedby the video encoder (603) in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ),and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source (601) may be astorage device storing previously prepared video. In a videoconferencingsystem, the video source (601) may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc. in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focuses on samples.

According to an embodiment, the video encoder (603) may code andcompress the pictures of the source video sequence into a coded videosequence (643) in real time or under any other time constraints asrequired by the application. Enforcing appropriate coding speed is onefunction of a controller (650). In some embodiments, the controller(650) controls other functional units as described below and isfunctionally coupled to the other functional units. The coupling is notdepicted for clarity. Parameters set by the controller (650) can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. The controller (650) can be configured to have other suitablefunctions that pertain to the video encoder (603) optimized for acertain system design.

In some embodiments, the video encoder (603) is configured to operate ina coding loop. As an oversimplified description, in an example, thecoding loop can include a source coder (630) (e.g., responsible forcreating symbols, such as a symbol stream, based on an input picture tobe coded, and a reference picture(s)), and a (local) decoder (633)embedded in the video encoder (603). The decoder (633) reconstructs thesymbols to create the sample data in a similar manner as a (remote)decoder also would create (as any compression between symbols and codedvideo bitstream is lossless in the video compression technologiesconsidered in the disclosed subject matter). The reconstructed samplestream (sample data) is input to the reference picture memory (634). Asthe decoding of a symbol stream leads to bit-exact results independentof decoder location (local or remote), the content in the referencepicture memory (634) is also bit exact between the local encoder andremote encoder. In other words, the prediction part of an encoder “sees”as reference picture samples exactly the same sample values as a decoderwould “see” when using prediction during decoding. This fundamentalprinciple of reference picture synchronicity (and resulting drift, ifsynchronicity cannot be maintained, for example because of channelerrors) is used in some related arts as well.

The operation of the “local” decoder (633) can be the same as of a“remote” decoder, such as the video decoder (510), which has alreadybeen described in detail above in conjunction with FIG. 5. Brieflyreferring also to FIG. 5, however, as symbols are available andencoding/decoding of symbols to a coded video sequence by an entropycoder (645) and the parser (520) can be lossless, the entropy decodingparts of the video decoder (510), including the buffer memory (515), andparser (520) may not be fully implemented in the local decoder (633).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

During operation, in some examples, the source coder (630) may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously coded picture fromthe video sequence that were designated as “reference pictures.” In thismanner, the coding engine (632) codes differences between pixel blocksof an input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder (633) may decode coded video data of picturesthat may be designated as reference pictures, based on symbols createdby the source coder (630). Operations of the coding engine (632) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 6), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (633) replicates decodingprocesses that may be performed by the video decoder on referencepictures and may cause reconstructed reference pictures to be stored inthe reference picture cache (634). In this manner, the video encoder(603) may store copies of reconstructed reference pictures locally thathave common content as the reconstructed reference pictures that will beobtained by a far-end video decoder (absent transmission errors).

The predictor (635) may perform prediction searches for the codingengine (632). That is, for a new picture to be coded, the predictor(635) may search the reference picture memory (634) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(635) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (635), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (634).

The controller (650) may manage coding operations of the source coder(630), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (645). The entropy coder (645)translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies such as Huffman coding, variable length coding, arithmeticcoding, and so forth.

The transmitter (640) may buffer the coded video sequence(s) as createdby the entropy coder (645) to prepare for transmission via acommunication channel (660), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(640) may merge coded video data from the video coder (603) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (650) may manage operation of the video encoder (603).During coding, the controller (650) may assign to each coded picture acertain coded picture type, which may affect the coding techniques thatmay be applied to the respective picture. For example, pictures oftenmay be assigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A bi-directionally predictive picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference picture. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (603) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (603) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (640) may transmit additional datawith the encoded video. The source coder (630) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, SEI messages, VUI parameter setfragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to intra prediction) makes use of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first reference picture and a secondreference picture that are both prior in decoding order to the currentpicture in the video (but may be in the past and future, respectively,in display order) are used. A block in the current picture can be codedby a first motion vector that points to a first reference block in thefirst reference picture, and a second motion vector that points to asecond reference block in the second reference picture. The block can bepredicted by a combination of the first reference block and the secondreference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC standard, apicture in a sequence of video pictures is partitioned into coding treeunits (CTU) for compression, the CTUs in a picture have the same size,such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTUincludes three coding tree blocks (CTBs), which are one luma CTB and twochroma CTBs. Each CTU can be recursively quadtree split into one ormultiple coding units (CUs). For example, a CTU of 64×64 pixels can besplit into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUsof 16×16 pixels. In an example, each CU is analyzed to determine aprediction type for the CU, such as an inter prediction type or an intraprediction type. The CU is split into one or more prediction units (PUs)depending on the temporal and/or spatial predictability. Generally, eachPU includes a luma prediction block (PB), and two chroma PBs. In anembodiment, a prediction operation in coding (encoding/decoding) isperformed in the unit of a prediction block. Using a luma predictionblock as an example of a prediction block, the prediction block includesa matrix of values (e.g., luma values) for pixels, such as 8×8 pixels,16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

FIG. 7 shows a diagram of a video encoder (703) according to anotherembodiment of the disclosure. The video encoder (703) is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder (703) is used in theplace of the video encoder (403) in the FIG. 4 example.

In an HEVC example, the video encoder (703) receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder (703) determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder (703) may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder(703) may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder (703) includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 7 example, the video encoder (703) includes the interencoder (730), an intra encoder (722), a residue calculator (723), aswitch (726), a residue encoder (724), a general controller (721), andan entropy encoder (725) coupled together as shown in FIG. 7.

The inter encoder (730) is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique. In some examples, thereference pictures are decoded reference pictures that are decoded basedon the encoded video information.

The intra encoder (722) is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform, and in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques). In an example, the intraencoder (722) also calculates intra prediction results (e.g., predictedblock) based on the intra prediction information and reference blocks inthe same picture.

The general controller (721) is configured to determine general controldata and control other components of the video encoder (703) based onthe general control data. In an example, the general controller (721)determines the mode of the block, and provides a control signal to theswitch (726) based on the mode. For example, when the mode is the intramode, the general controller (721) controls the switch (726) to selectthe intra mode result for use by the residue calculator (723), andcontrols the entropy encoder (725) to select the intra predictioninformation and include the intra prediction information in thebitstream; and when the mode is the inter mode, the general controller(721) controls the switch (726) to select the inter prediction resultfor use by the residue calculator (723), and controls the entropyencoder (725) to select the inter prediction information and include theinter prediction information in the bitstream.

The residue calculator (723) is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder (722) or the inter encoder (730). Theresidue encoder (724) is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder (724) is configured to convert the residuedata from a spatial domain to a frequency domain, and generate thetransform coefficients. The transform coefficients are then subject toquantization processing to obtain quantized transform coefficients. Invarious embodiments, the video encoder (703) also includes a residuedecoder (728). The residue decoder (728) is configured to performinverse-transform, and generate the decoded residue data. The decodedresidue data can be suitably used by the intra encoder (722) and theinter encoder (730). For example, the inter encoder (730) can generatedecoded blocks based on the decoded residue data and inter predictioninformation, and the intra encoder (722) can generate decoded blocksbased on the decoded residue data and the intra prediction information.The decoded blocks are suitably processed to generate decoded picturesand the decoded pictures can be buffered in a memory circuit (not shown)and used as reference pictures in some examples.

The entropy encoder (725) is configured to format the bitstream toinclude the encoded block. The entropy encoder (725) is configured toinclude various information according to a suitable standard, such asthe HEVC standard. In an example, the entropy encoder (725) isconfigured to include the general control data, the selected predictioninformation (e.g., intra prediction information or inter predictioninformation), the residue information, and other suitable information inthe bitstream. Note that, according to the disclosed subject matter,when coding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 8 shows a diagram of a video decoder (810) according to anotherembodiment of the disclosure. The video decoder (810) is configured toreceive coded pictures that are part of a coded video sequence, anddecode the coded pictures to generate reconstructed pictures. In anexample, the video decoder (810) is used in the place of the videodecoder (410) in the FIG. 4 example.

In the FIG. 8 example, the video decoder (810) includes an entropydecoder (871), an inter decoder (880), a residue decoder (873), areconstruction module (874), and an intra decoder (872) coupled togetheras shown in FIG. 8.

The entropy decoder (871) can be configured to reconstruct, from thecoded picture, certain symbols that represent the syntax elements ofwhich the coded picture is made up. Such symbols can include, forexample, the mode in which a block is coded (such as, for example, intramode, inter mode, bi-predicted mode, the latter two in merge submode oranother submode), prediction information (such as, for example, intraprediction information or inter prediction information) that canidentify certain sample or metadata that is used for prediction by theintra decoder (872) or the inter decoder (880), respectively, residualinformation in the form of, for example, quantized transformcoefficients, and the like. In an example, when the prediction mode isinter or bi-predicted mode, the inter prediction information is providedto the inter decoder (880); and when the prediction type is the intraprediction type, the intra prediction information is provided to theintra decoder (872). The residual information can be subject to inversequantization and is provided to the residue decoder (873).

The inter decoder (880) is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder (872) is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder (873) is configured to perform inverse quantizationto extract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder (873) mayalso require certain control information (to include the QuantizerParameter (QP)), and that information may be provided by the entropydecoder (871) (data path not depicted as this may be low volume controlinformation only).

The reconstruction module (874) is configured to combine, in the spatialdomain, the residual as output by the residue decoder (873) and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders (403), (603), and (703), and thevideo decoders (410), (510), and (810) can be implemented using anysuitable technique. In an embodiment, the video encoders (403), (603),and (703), and the video decoders (410), (510), and (810) can beimplemented using one or more integrated circuits. In anotherembodiment, the video encoders (403), (603), and (603), and the videodecoders (410), (510), and (810) can be implemented using one or moreprocessors that execute software instructions.

Aspects of the disclosure provide techniques for matrix based intraprediction.

FIG. 9 shows an illustration of exemplary intra prediction directionsand the intra prediction modes used in HEVC. In HEVC, there are total 35intra prediction modes (mode 0 to mode 34). The mode 0 and mode 1 arenon-directional modes, among which mode 0 is planar mode and mode 1 isDC mode. The DC mode uses an average of all samples. The planar modeuses an average of two linear predictions. The modes 2-34 aredirectional modes, among which mode 10 is horizontal mode, mode 26 isvertical mode, and mode 2, mode 18 and mode 34 are diagonal modes. Insome examples, the intra prediction modes are signaled by three mostprobable modes (MPMs) and 32 remaining modes.

FIG. 10 shows an illustration of exemplary intra prediction directionsand intra prediction modes in some examples (e.g., VVC). There are total95 intra prediction modes (mode −14 to mode 80), among which mode 18 ishorizontal mode, mode 50 is vertical mode, and mode 2, mode 34 and mode66 are diagonal modes. Modes −1˜−14 and Modes 67−80 are calledwide-angle intra prediction (WAIP) modes (also referred to aswide-angular modes, wide angular direction modes and the like).

In the present disclosure, the direction based intra prediction isreferred to as regular intra prediction or non-matrix based intraprediction.

According to some aspects of the disclosure, an intra prediction modethat is referred to as affine linear weighted intra prediction (ALWIP)mode can be used. ALWIP can be also referred to as matrix based intraprediction (MIP). For example, in a version of joint video explorationteam (JVET), ALWIP (matrix based intra prediction) can be used toimprove the performance of intra prediction process.

Specifically, for predicting the samples of a rectangular block of widthW and height H, matrix based intra prediction takes one left column of Hreconstructed neighboring boundary samples of the block (denoted bybdry^(left)) and one above row of W reconstructed neighboring boundarysamples of the block (denoted by bdry^(top)) as input. When thereconstructed samples are unavailable, certain intra predictiontechniques, such as padding techniques, can be used to generate paddingsamples in the bdry^(left) and bdry^(top). Then, the samples of arectangular block of width W and height H rectangular can be generatedbased on three steps. The generation of the prediction signal is basedon following three steps.

In a first step, out of the boundary samples, four samples in the caseof W=H=4, and eight samples in all other cases are extracted based onaveraging neighboring samples. The 4 or 8 extracted samples can bereferred to as a subsampled set of samples in the original block.

In a second step, a matrix vector multiplication, followed by additionof an offset, can be carried out with the averaged samples as an input.The result is a reduced prediction signal on the subsampled set ofsamples in the original block.

In a third step, the prediction signal at the remaining positions isgenerated from the reduced prediction signal on the subsampled set bylinear interpolation in each direction.

More specifically, in the first step, the numbers of the neighboringboundary samples of the above row and the left column bdry^(top) andbdry^(left) are reduced by averaging neighboring samples. The reducedneighboring boundary samples of the above row can be referred bybdry_(red) ^(top) and reduced neighboring boundary samples of the leftcolumn can be referred by bdry_(red) ^(left).

It is noted that when the current block is 4×4 block, the reducedneighboring boundary samples of the above row bdry_(red) ^(top) includes2 samples, and the reduced neighboring boundary samples of the leftcolumn bdry_(red) ^(left) includes 2 samples. For other cases (e.g., W>4and H>4), the reduced neighboring boundary samples of the above rowbdry_(red) ^(top) includes 4 samples, and the reduced neighboringboundary samples of the left column bdry_(red) ^(left) includes 4samples.

In the case of a 4×4-block, for 0≤i<2, the reduced neighboring boundarysamples of the above row can be defined according to (Eq. 1), thereduced neighboring boundary samples of the left column can be definedsimilarly.

$\begin{matrix}{{{bdry}_{red}^{top}\lbrack i\rbrack} = {\left( {\left( {\sum_{j = 0}^{1}{{bdry}^{top}\left\lbrack {{i \cdot 2} + j} \right\rbrack}} \right) + 1} \right) ⪢ 1}} & \left( {{Eq}.\mspace{11mu} 1} \right)\end{matrix}$

In the cases that the block width W is given as W=4·2^(k), for 0≤i<4,the reduced neighboring boundary samples of the above row can be definedaccording to (Eq. 2), the reduced neighboring boundary samples of theleft column can be defined similarly.

$\begin{matrix}{{{bdry}_{red}^{top}\lbrack i\rbrack} = {\left( {\left( {\sum_{j = 0}^{1}{{bdry}^{top}\left\lbrack {{i \cdot 2} + j} \right\rbrack}} \right) + \left( {1 ⪡ \left( {k - 1} \right)} \right)} \right) ⪢ k}} & \left( {{Eq}.\mspace{11mu} 2} \right)\end{matrix}$

Further, in the first step, the bdry_(red) ^(top) and bdry_(red) ^(left)are concatenated to form bdry_(red), which is a vector that can include4 or 8 elements.

Specifically, in the second step, the reduced prediction signalpred_(red) is computed by calculating a matrix vector product and addingan offset, such as according to (Eq. 3):

$\begin{matrix}{{pred}_{red} = {{A \cdot {bdry}_{red}} + {b.}}} & \left( {{Eq}.\mspace{11mu} 3} \right)\end{matrix}$

where A denotes a matrix and b denotes a vector.

The matrix A and the vector b are taken from one of the sets S₀, S₁, S₂,where the subscript of a set idx(W, H) is derived as (Eq. 4):

$\begin{matrix}{{{idx}\left( {W,H} \right)} = \left\{ \begin{matrix}0 & {{{for}\mspace{14mu} W} = {H = 4}} \\1 & {{{for}\mspace{14mu}{\max\left( {W,H} \right)}} = 8} \\2 & {{{{for}\mspace{14mu}{\max\left( {W,H} \right)}} > 8},}\end{matrix} \right.} & \left( {{Eq}.\mspace{11mu} 4} \right)\end{matrix}$

The set S₀ includes 18 matrices A₀ ^(i), i∈{0, . . . , 17} each of whichhas 16 rows and 4 columns, and 18 offset vectors b₀ ^(i), i∈{0, . . . ,17} each of which is with size 16. Matrices and offset vectors of thatset are used for blocks of size 4×4. The set S₁ includes of 10 matricesA₁ ^(i), i∈{0, . . . , 9}, each of which has 16 rows and 8 columns and10 offset vectors b₁ ^(i), i∈{0, . . . , 9} each of which is with size16. Matrices and offset vectors of that set are used for blocks of sizes4×8, 8×4 and 8×8. Finally, the set S₂ consists of 6 matrices A₂ ^(i),i∈{0, . . . , 5}, each of which has 64 rows and 8 columns and of 6offset vectors b₂ ^(i), i∈{0, . . . , 5} of size 64. Matrices and offsetvectors of that set or parts of these matrices and offset vectors areused for all other block-shapes.

Specifically, in the third step, for a W×H block with max(W, H)≥8, theprediction signal can be generated from the reduced prediction signalpred_(red) on W_(red)×H_(red) by linear interpolation. Depending on theblock shape, linear interpolation can be performed in verticaldirection, horizontal direction or both directions. If linearinterpolation is to be applied in both directions, the linearinterpolation can be first applied in horizontal direction when W<H andcan be first applied in vertical direction when W≥H.

In an example (without loss of generality), a W×H block with max(W, H)≥8and W≥H. The linear interpolation can be performed as follows. First,the reduced prediction signal is extended to the top by the boundarysignal. The extended reduced prediction signal can be defined by (Eq. 5)

$\begin{matrix}{{{{pred}_{red}\lbrack x\rbrack}\left\lbrack {- 1} \right\rbrack} = {{bdry}^{top}\lbrack x\rbrack}} & \left( {{Eq}.\mspace{11mu} 5} \right)\end{matrix}$

Then, from this extended reduced prediction signal, the verticallylinear interpolated prediction signal is generated by (Eq. 6):

$\begin{matrix}{{{{pred}_{red}^{{up},{ver}}\lbrack x\rbrack}\left\lbrack {{U_{ver} \cdot y} + k} \right\rbrack} = {\left( {{\left( {U_{ver} - k - 1} \right) \cdot {{{pred}_{red}\lbrack x\rbrack}\left\lbrack {y - 1} \right\rbrack}} + {\left( {k + 1} \right) \cdot {{{pred}_{red}\lbrack x\rbrack}\lbrack y\rbrack}} + \frac{U_{ver}}{2}} \right) ⪢ U_{ver}}} & \left( {{Eq}.\mspace{14mu} 6} \right)\end{matrix}$

for 0≤x<W_(red), 0≤y<H_(red) and 0≤k<U_(ver), where W_(red) denotes thereduced width of the reduced prediction signal, H_(red) denotes thereduced height of the reduced prediction signal, U_(ver) denotes theratio of height (of the block) to the reduced height (of the reducedprediction signal).

It is noted that, in some examples, horizontal linear interpolation canbe similarly performed.

Using an 8×8 block as an example, FIG. 11-13 show the three steps ofmatrix based intra prediction.

FIG. 11 shows a diagram illustrating the first step of matrix basedintra prediction in some examples. In the FIG. 11 example, the currentblock is a 8×8 block. Thus, the left column of the current blockincludes 8 reconstructed neighboring boundary samples that are referredby bdry^(left); the above row of the current block includes 8reconstructed neighboring boundary samples that are referred bybdry^(top). In the first step, the numbers of the neighboring boundarysamples of the above row and the left column bdry^(top) and bdry^(left)are reduced by averaging neighboring samples as shown in FIG. 11. Forexample, the number of neighboring boundary samples of the above rows isreduced from 8 to 4, and the number of neighboring boundary samples ofthe left column is reduced from 8 to 4. The reduced neighboring boundarysamples of the above row can be referred by bdry_(red) ^(top) andreduced neighboring boundary samples of the left column can be referredby bdry_(red) ^(left).

The reduced neighboring boundary samples of the above row and the leftcolumn are concatenated to form a vector of 8 samples.

FIG. 12 shows a diagram illustrating the second step of matrix basedintra prediction in some examples. In the second step, the vector of 8entries is input to a matrix vector multiplication. The matrix is takenfrom the set S₁. The output of the matrix vector multiplication includesa vector of 16 samples that are samples for the odd positions of theprediction block. In an example, a total of (8·16)/(8·8)=2multiplications per sample are performed. It is noted that offsets arealso added to the samples.

FIG. 13 shows a diagram illustrating the third step of matrix basedintra prediction. After the second steps, 16 samples that are samplesfor the odd positions (e.g., dark positions in left part of FIG. 13) ofthe prediction block. In the FIG. 13 example, the 16 samples areinterpolated vertically by using the reduced top boundary. Then,horizontal interpolation can be performed by using the original leftboundary. It is noted that in the example of 8×8 block, theinterpolation process can be performed using addition and shiftingoperations and does not require any multiplication operations.

According to an aspect of the disclosure, the above matrix based intraprediction can be suitably modified for various benefits, such as easyconvergence, saving storage space, and the like.

In some examples (e.g., JVET-00481), residue signals of the reducedneighboring boundary samples for better convergence. For example, afteraveraging boundary samples, one additional step to obtain residuesignals is performed, and the residue signals can be used in the placeof the reduced neighboring boundary samples to achieve easy convergence.

For example, when idx(W, H)=0 or idx(W, H)=1, then (Eq. 7)-(Eq. 8) areperformed:

$\begin{matrix}{{{{input}_{ref}\lbrack 0\rbrack} = {{{bdry}_{red}\lbrack 0\rbrack} - \left( {1 ⪡ \left( {{bitDepth} - 1} \right)} \right)}},} & \left( {{Eq}.\mspace{11mu} 7} \right) \\{{{{input}_{red}\lbrack j\rbrack} = {{{bdry}_{red}\lbrack j\rbrack} - {{bdry}_{red}\lbrack 0\rbrack}}},{j = 1},\ldots\;,{{{size}\left( {bdry}_{red} \right)} - 1},} & \left( {{Eq}.\mspace{11mu} 8} \right)\end{matrix}$

Otherwise, when idx(W, H)=2, (Eq. 9) can be performed:

$\begin{matrix}{{{{input}_{red}\lbrack j\rbrack} = {{{bdry}_{red}\left\lbrack {j + 1} \right\rbrack} - {{bdry}_{red}\lbrack 0\rbrack}}},{j = 1},\ldots\;,{{{size}\left( {bdry}_{red} \right)} - 2},} & \left( {{Eq}.\mspace{11mu} 9} \right)\end{matrix}$

It is noted that bitDepth denotes the luma bit-depth. Thus, for idx(W,H)=0 or idx(W, H)=1, input_(red) is of the same size (inSize) asbdry_(red) and, when idx(W, H)=2, size inSize=size(bdry_(red))−1. Forexample, when internal bit-depth is set equal to 10, the bit depth ofbdry_(red)[i] is 10, and the bit depth of input_(red)[j] is 11 sinceit's generated by subtracting one 10-bit value from another 10-bitvalue.

Further, in some embodiments, a matrix A is selected based on the MIPmode. In some examples, the sets S₀, S₁, S₂ of matrices arepre-determined based on training, and are suitably stored. In someembodiments, the sets S₂ can be stored with some rows left out to savestorage space.

The set S₀ consists of 18 matrices A₀ ^(i), i∈{0, . . . , 17} each ofwhich has 16 rows and 4 columns. Matrices of set S₀ are used if idx(W,H)=0, i.e., for blocks of size 4×4. The set S₁ consists of 10 matricesA₁ ^(i), i∈{0, . . . , 9}, each of which has 16 rows and 8 columns.Matrices of that set are used if idx(W, H)=1, i.e., for blocks of sizes4×8, 8×4 and 8×8.

It is noted that, the matrices in the set S₂ can be similarly processedas in (Eq. 9), to make the first column in the matrices to be zero, andthen do not need to be stored. Thus, the set S₂ consists of 6 matricesA₂ ^(i), i∈{0, . . . , 5}, each of which has 64 rows and 7 columns.Matrices of set S₂ or parts of these matrices are used if idx(W, H)=2,i.e., for all other block-shapes.

According to an aspect of the disclosure, entries of the matricesbelonging to the sets S₀, S₁ and S₂ can be converted to unsigned numbersbased on factors fW (e.g., a factor fW for a matrix can be set as anabsolute value of the minimum entries in the matrix) and thus can bestored as unsigned numbers. In some examples, the entries of thematrices belonging to the sets S₀, S₁ and S₂ can be stored in 7 bits asunsigned 7-bit numbers, and the factors fW are stored as 7-bit numbers.

In some examples, W_(red) and H_(red) denote the width and the height ofthe reduced prediction signal and sW denotes the shift corresponding tothe prediction mode, the reduced prediction signal pred_(red) can becalculated according to (Eq. 10):

$\begin{matrix}{{{{pred}_{red}\lbrack i\rbrack} = {\left( {\left( {\left( {\sum_{j = 0}^{inSize}{\left( {{{A\lbrack i\rbrack}\lbrack j\rbrack} - {fW}} \right) \cdot {{input}_{red}\lbrack j\rbrack}}} \right) + \left( {1 ⪡ \left( {{sW} - 1} \right)} \right)} \right) ⪢ {sW}} \right) + {{bdry}_{red}\lbrack 0\rbrack}}},{{{where}\mspace{14mu} i} \in {\left\{ {0,\ldots\;,{{W_{red} \cdot H_{red}} - 1}} \right\}.}}} & \left( {{Eq}.\mspace{11mu} 10} \right)\end{matrix}$

In an example, the entries A[i][j] and the factors f W are storedseparately (the matrix-vector product can be computed as in JVET-00084),then, the entries A[i][j] and the factors fW can both be stored in 7bits. In another example, the differences (A[i][j]−fW) can be stored in8 bits.

In some examples, techniques of internal bit depth increase or decreasecan be used. For example, when the input source is 10 bit, and eachsource sample is scaled to an 8-bit value prior to encoding in a processcalled internal bit depth decrease (IBDD). This scaling is obtained byapplying the function y=(x+2)/4 to the input value x and clipping theresult y to the [0,255] range. Oppositely, when the input is an 8-bitsource, each sample is scaled to 10-bit value before encoding byapplying the y=4×x function to the input values x. This process iscalled internal bit depth increase (IBDI), and it allows higherprecision in the internal video codec operations (improved encodingefficiency) at the cost of an increase in memory requirements, mainly tostore reference picture in the decoded picture buffer (DPB), and also anincrease of arithmetic bit-depth.

According to an aspect of the disclosure, for matrix based intraprediction (MIP) prediction process, the most time-consuming operationis the multiplication operations in the matrix vector multiplication.For example, a multiplication operation can be represented byA[i][j]·input_(red)[j]. It is noted that in some examples, A[i][j] canbe 7-bit unsigned and input_(red)[j] can be 9-bit signed (when internalbit depth is set to 8 and because of usage of Eqs. 7-9) or 11-bit signed(when internal bit depth is set to 10 and because of usage of Eqs. 7-9).Since the bit depth of input_(red) [j] is greater than 8-bit, 16-bitmultiplications are required for MIP prediction process, which is notdesirable in some examples. The present disclosure can providetechniques to avoid the usage of 16-bit multiplications.

According to another aspect of the disclosure, the boundary referencesample averaging process is a different intra reference sample filteringprocess from regular intra prediction mode. The coding gain of the addedprocess may not justify the added complexity. The present disclosure canprovide techniques to conform the boundary reference sample averagingprocess with the regular intra prediction mode.

According to another aspect of the disclosure, the variable fW is a7-bit unsigned value, and for each block, 7 or 8 multiplications areused to compute the following expressions Σ_(j=0)^(inSize)fW·input_(red)[j]. The present disclosure can providetechniques to avoid the multiplication operations.

According to another aspect of the disclosure, the size of generatedreduced predicted samples is 4×4 or 8×8. When width and height ofcurrent block are larger than 16, the added additional multiplicationsper sample (e.g., using Eq. 6 for interpolation) is around 2.Especially, when current CU is 64×64, total number of addedmultiplications is around 64×64×2=8192. The coding gain of this addedprocess may not justify complexity.

The proposed methods may be used separately or combined in any order.Further, each of the methods (or embodiments), encoder, and decoder maybe implemented by processing circuitry (e.g., one or more processors orone or more integrated circuits). In one example, the one or moreprocessors execute a program that is stored in a non-transitorycomputer-readable medium.

According to an aspect of the disclosure, the residues of reducedboundary samples input_(red)[j] in (Eq. 7)-(Eq. 9) can be suitablyconverted to 8-bit values before the matrix multiplication process, thus8-bit multiplications (instead of the 16-bit multiplications) can beused. In some examples, the residues of reduced boundary samplesinput_(red) [j] in (Eq. 7)-(Eq. 9) can be right shifted or/and clippedto 8-bit value before the matrix multiplication process.

In an embodiment, the reduced boundary samples input_(red) [j] is rightshifted or/and clipped to 8-bit value before the matrix multiplicationprocess when the bit depth of input source and/or internal bit depth isless than or equal to K. K is a positive integer, such as 8, 10, or 12.

In an example, the residues of reduced boundary samples input_(red)[j]is right shifted to 8-bit value using the following (Eq. 11)-(Eq. 13),and weight shift variable sW is subtracted by (bithdepth+1−8) to alignwith the bit depth of output of the matrix multiplication process asshown in (Eq. 14).

For example, when idx(W, H)=0 or idx(W, H)=1, (Eq. 11)-(Eq. 12) can beused to convert the residues of the reduced boundary sample inputs:

$\begin{matrix}{{{input}_{red}\lbrack 0\rbrack} = {\left( {{{bdry}_{red}\lbrack 0\rbrack} - \left( {1 ⪡ \left( {{bitDepth} - 1} \right)} \right)} \right) ⪢ \left( {{bithdepth} + 1 - 8} \right)}} & \left( {{Eq}.\mspace{11mu} 11} \right) \\{{{{input}_{red}\lbrack j\rbrack} = {\left( {{{bdry}_{red}\lbrack j\rbrack} - {{bdry}_{red}\lbrack 0\rbrack}} \right) ⪢ \left( {{bithdepth} + 1 - 8} \right)}},{j = 1},\ldots\;,{{{size}\left( {bdry}_{red} \right)} - 1},} & \left( {{Eq}.\mspace{11mu} 12} \right)\end{matrix}$

Otherwise, when idx(W, H)=2, (Eq. 13) can be used to convert theresidues of the reduced boundary sample inputs:

$\begin{matrix}{{{{input}_{red}\lbrack j\rbrack} = {\left( {{{bdry}_{red}\left\lbrack {j + 1} \right\rbrack} - {{bdry}_{red}\lbrack 0\rbrack}} \right) ⪢ \left( {{bithdepth} + 1 - 8} \right)}},{j = 0},\ldots\;,{{{size}\left( {bdry}_{red} \right)} - 2},} & \left( {{Eq}.\mspace{11mu} 13} \right) \\{{sW} = {{sW} - \left( {{BitDepth} + 1 - 8} \right)}} & \left( {{Eq}.\mspace{11mu} 14} \right)\end{matrix}$

In another example, the reduced boundary samples input_(red) [j] isclipped to range of 8-bit using the following (Eq. 15)-(Eq. 17).

For example, when idx(W, H)=0 or idx(W, H)=1, then (Eq. 15)-(Eq. 16) canbe used to convert the residues of the reduced boundary sample inputs:

$\begin{matrix}{{{input}_{red}\lbrack 0\rbrack} = {{clip}\left( {{- 128},127,{{{bdry}_{red}\lbrack 0\rbrack} - \left( {1 ⪡ \left( {{bitDepth} - 1} \right)} \right)}} \right)}} & \left( {{Eq}.\mspace{11mu} 15} \right) \\{{{{input}_{red}\lbrack j\rbrack} = {{clip}\left( {{- 128},127,{{{bdry}_{red}\lbrack j\rbrack} - {{bdry}_{red}\lbrack 0\rbrack}}} \right)}},{j = 1},\ldots\;,{{{size}\left( {bdry}_{red} \right)} - 1}} & \left( {{Eq}.\mspace{11mu} 16} \right)\end{matrix}$

Otherwise, in an example, when idx(W, H)=2, then (Eq. 17) can be used toconvert the residues of the reduced boundary sample inputs:

$\begin{matrix}{{{{input}_{red}\lbrack j\rbrack} = {{clip}\left( {{- 128},127,{{{bdry}_{red}\left\lbrack {j + 1} \right\rbrack} - {{bdry}_{red}\lbrack 0\rbrack}}} \right)}},{j = 0},\ldots\;,{{{size}\left( {bdry}_{red} \right)} - 2},} & \left( {{Eq}.\mspace{11mu} 17} \right)\end{matrix}$

In another example, the reduced boundary samples input_(red)[j] is firstclipped to range of (N−L) bit, and then right shifted to 8 bit. Ndenotes the internal bit depth, L is a positive integer and L is smallerthan (N−8), such as 1 or 2. Weight shift variable sW is subtracted by(bithdepth+1−8−L) to align with the bit depth of output of the matrixmultiplication process.

In some embodiments, the residues of reduced boundary samplesinput_(red) [j] in (Eq. 10) is right shifted by M bits before the matrixmultiplication process, example values of M is 1, 2 or 3.

In an embodiment, M is a fixed value regardless of bit depth of inputsource and/or internal bit depth. In an example, M is fixed to 1regardless of bit depth of input source and/or internal bit depth. In anexample, M is fixed to 2 regardless of bit depth of input source and/orinternal bit depth. In an example, M is fixed to 3 regardless of bitdepth of input source and/or internal bit depth.

In another embodiment, M can be a configurable value, and the value issignaled in the high level syntax, including, but not limited to SPS,VPS, PPS, APS, or slice header.

In another embodiment, M depends on internal bit depth of the codec. Inan example, M is defined by a look-up table, indexed by the internal bitdepth. Given the internal bit depth value, the value of M can be derivedbased on the look-up table that is predefined. In another example, M isdefined by a look-up table, indexed by the internal bit depth, and thelook-up table can be signaled in the high level syntax, including, butnot limited to SPS, VPS, PPS, APS, or slice header.

In another embodiment, the reduced boundary samples input_(red)[j] isright shifted or/and clipped to 8-bit value before the matrixmultiplication process when bit depth of input source and/or internalbit depth is 8.

In another embodiment, the reduced boundary samples input_(red)[j] isright shifted by 1 bit before the matrix multiplication process when bitdepth of input source and/or internal bit depth greater than 8.

According to an aspect of the disclosure, the matrix based intraprediction can use the same reference sample filtering (or smoothing)process as regular intra prediction.

In an embodiment, for 4×4 (or 4×8 or 8×4) blocks, reference samplefiltering process (e.g., averaging step) is disabled for MIP modes. Thereduced boundary samples can be selected from certain positions.

In another embodiment, 3-tap [1,2,1] reference sample smoothing filterthat is used for regular intra prediction process can be used in theplace of the reference sample averaging process of MIP modes.

In some examples, when width (or height) of current CU is greater than4, after reference sample filtering process (e.g., using 3-tap [1,2,1]reference sample smoothing filter), the filtered reference samples at([1/4, 2/4, 3/4, 4/4]×width) (or [1/4, 2/4, 3/4, 4/4]×height) positionsfor above (or left) neighboring samples are picked as the reducedboundary samples, denoted by bdry_(red)[i].

In some examples, when width (or height) of current CU is greater than4, after reference sample filtering process, the filtered referencesamples at ([1/8, 3/8, 5/8, 7/8]×width) (or [1/8, 3/8, 5/8, 7/8]-height)positions respectively for above (or left) neighboring samples arepicked as the reduced boundary samples, denoted by bdry_(red)[i].

FIG. 14 shows a diagram of a current block having a size of 8×8 andneighboring samples. In the FIG. 14 example, the neighboring samples at([1/8, 3/8, 5/8, 7/8]×width) positions in above neighboring row and([1/8, 3/8, 5/8, 7/8]×height) positions in left neighboring column aremarked with grey color. In an example, after reference sample filteringprocess, the neighboring samples at the grey color positions areselected as the reduced boundary samples.

FIG. 15 shows a diagram of a current block having a size of 16×16 andneighboring samples. In the FIG. 15 example, the neighboring samples at([1/8, 3/8, 5/8, 7/8]×width) positions in above neighboring row and([1/8, 3/8, 5/8, 7/8]×height) positions in left neighboring column aremarked with grey color. In an example, after reference sample filteringprocess, the neighboring samples at the grey color positions areselected as the reduced boundary samples.

In another example, when the current block has a size of 4×4, afterreference sample filtering process, the filtered reference samples at([2/4, 4/4]×width) or ([1/4, 3/4]×width) for the above neighboringsamples can be selected and then filtered reference samples at ([2/4,4/4]×height) or [1/4, 3/4]×height) positions for left neighboringsamples can be selected as the reduced boundary samples, denoted bybdry_(red)[i].

In another example, when width (or height) of current block is greaterthan 8, after reference sample filtering process, the filtered referencesamples at ([3/16, 7/16, 11/16, 15/16]×width) (or [3/16, 7/16, 11/16,15/16]×height) positions for above (or left) neighboring samples areselected as the reduced boundary samples, denoted by bdry_(red)[i].

According to another aspect of the disclosure, for MIP predictionprocess, the above neighboring samples and the left neighboring samplescan be processed respectively with or without filtering or averaging. Insome embodiments, the above neighboring samples are filtered oraveraged, but left neighboring samples are not filtered or averaged. Thesamples at left neighboring column can be directly selected to form thereduced left boundary samples.

In an embodiment, for MIP prediction process, the above neighboringsamples are filtered or averaged, but left neighboring samples are notfiltered or averaged, and samples at [1/4, 2/4,3/4,4/4]×height positionsor [1/2,2/2]×height positions are directly picked to form the reducedleft boundary samples.

In another embodiment, for above neighboring samples, the reducedsamples are derived by averaging two samples of every (width/8) sampleof the original above boundary when width is equal to or greater than 8.

In another embodiment, for above neighboring samples, the reducedsamples are set equal to the original above boundary when width is equalto 4.

According to another aspect of the disclosure, reference sampleaveraging process for MIP mode is disabled when the current block sizeis 4×4 (or 4×8 or 8×4). In an embodiment, the un-filtered referencesamples at ([1/4, 2/4, 3/4, 4/4]×width) (or [1/4, 2/4, 3/4, 4/4]×height)positions for above (or left) neighboring samples are directly picked asthe reduced boundary samples, denoted by bdry_(red)[0] when currentblock size is 4×4 (or 4×8 or 8×4).

According to another aspect of the disclosure, for the up-samplinginterpolation process of MIP modes, the prediction signal at theremaining positions are set equal to the average of its two adjacentreduced prediction samples for all block sizes. Here, the remainingpositions denote the sample positions whose prediction signal are notgenerated through matrix multiplication process, and needs to beinterpolated through up-sampling process. The average operation can beperformed by right shifting 1 bit. Thus, no more multiplicationoperation is needed in the up-sampling operation.

According to another aspect of the disclosure, the value of variable f Wis modified to power of 2 for block sizes and all MIP modes. Therefore,additions and shifts can be used to compute the following expressionsΣ_(j=0) ^(inSize) fW·input_(red)[j], no multiplication operation isneeded.

FIG. 16 shows a flow chart outlining a process (1600) according to anembodiment of the disclosure. The process (1600) can be used in thereconstruction of a block, so to generate a prediction block for theblock under reconstruction. In various embodiments, the process (1600)are executed by processing circuitry, such as the processing circuitryin the terminal devices (310), (320), (330) and (340), the processingcircuitry that performs functions of the video encoder (403), theprocessing circuitry that performs functions of the video decoder (410),the processing circuitry that performs functions of the video decoder(510), the processing circuitry that performs functions of the videoencoder (603), and the like. In some embodiments, the process (1600) isimplemented in software instructions, thus when the processing circuitryexecutes the software instructions, the processing circuitry performsthe process (1600). The process starts at (S1601) and proceeds to(S1610).

At (S1610), prediction information of a block is decoded from a codedvideo bitstream. The prediction information is indicative of a matrixbased intra prediction for the block.

At (S1620), entries of a vector are determined based on neighboringsamples of the block. In an example, each entry is determined based onone or more neighboring samples of the block.

In an example, a filtering tool is used to determine the entries of thevector based on the neighboring samples of the block. The filtering toolcan be the same one used in a non-matrix based intra prediction (e.g.,regular intra prediction).

In another example, a subset of the neighboring samples of the block isselected as the entries of the vector based on positions of theneighboring samples with reference to the block.

In another example, a first portion of the entries of the vector isdetermined based on filtering first neighboring samples on a first sideof the block, and a second portion of the entries of the vector isselected from second neighboring samples on a second side of the block.

At (S1630), the entries of the vector are converted into a reduced bitform with a number of bits satisfying a requirement of using a firstmultiplication tool that processes fewer bits than a secondmultiplication tool.

In an example, the entries of the vector are right shifted by one ormore bits. In another example, the entries of the vector are clippedinto a range corresponding to fewer bits. In another example, theentries of the vector are first clipped and then right-shifted. In someexamples, a weight shifting variable that is used for aligningmultiplication results is modified based on the number of bits in theright-shifting.

In an example, the number of bits to shift is determined based on aninternal bit depth. In another example, the number of bits to shift isdetermined based on a signal in a high level syntax. In another example,the number of bits to shift is determined based on a look-up tableindexed. In another example, a lookup table can be decoded from a highlevel syntax, and the number of bits is determined from the lookup tablewhich is indexed by an internal bit depth.

In some embodiments, the entries of the matrix are adjusted to unify theentries of the matrix to have a same sign based on a factor parameterfW. The factor parameter fW has an integer value that is a power of two(e.g., 64, 128).

At (S1640), the entries of the vector in the reduced bit form aremultiplied, using the first multiplication tool, with entries of amatrix to calculate a subset of prediction samples of the block.

At (S1650), other prediction samples of the block are determined basedon the subset of the prediction samples of the block. In an embodiment,one or more other prediction samples between two prediction samples inthe subset are determined based on the two samples, such as a linearinterpolation of the two samples. In another embodiment, one or moreother prediction samples between two prediction samples in the subsetare determined based on an average of the two samples. Then, the processproceeds to (S1699) and terminates.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 17 shows a computersystem (1700) suitable for implementing certain embodiments of thedisclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 17 for computer system (1700) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (1700).

Computer system (1700) may include certain human interface inputdevices. Such a human interface input device may be responsive to inputby one or more human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (1701), mouse (1702), trackpad (1703), touchscreen (1710), data-glove (not shown), joystick (1705), microphone(1706), scanner (1707), camera (1708).

Computer system (1700) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (1710), data-glove (not shown), or joystick (1705), butthere can also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers (1709), headphones(not depicted)), visual output devices (such as screens (1710) toinclude CRT screens, LCD screens, plasma screens, OLED screens, eachwith or without touch-screen input capability, each with or withouttactile feedback capability-some of which may be capable to output twodimensional visual output or more than three dimensional output throughmeans such as stereographic output; virtual-reality glasses (notdepicted), holographic displays and smoke tanks (not depicted)), andprinters (not depicted).

Computer system (1700) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(1720) with CD/DVD or the like media (1721), thumb-drive (1722),removable hard drive or solid state drive (1723), legacy magnetic mediasuch as tape and floppy disc (not depicted), specialized ROM/ASIC/PLDbased devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (1700) can also include an interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (1749) (such as, for example USB ports of thecomputer system (1700)); others are commonly integrated into the core ofthe computer system (1700) by attachment to a system bus as describedbelow (for example Ethernet interface into a PC computer system orcellular network interface into a smartphone computer system). Using anyof these networks, computer system (1700) can communicate with otherentities. Such communication can be uni-directional, receive only (forexample, broadcast TV), uni-directional send-only (for example CANbus tocertain CANbus devices), or bi-directional, for example to othercomputer systems using local or wide area digital networks. Certainprotocols and protocol stacks can be used on each of those networks andnetwork interfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (1740) of thecomputer system (1700).

The core (1740) can include one or more Central Processing Units (CPU)(1741), Graphics Processing Units (GPU) (1742), specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)(1743), hardware accelerators for certain tasks (1744), and so forth.These devices, along with Read-only memory (ROM) (1745), Random-accessmemory (1746), internal mass storage such as internal non-useraccessible hard drives, SSDs, and the like (1747), may be connectedthrough a system bus (1748). In some computer systems, the system bus(1748) can be accessible in the form of one or more physical plugs toenable extensions by additional CPUs, GPU, and the like. The peripheraldevices can be attached either directly to the core's system bus (1748),or through a peripheral bus (1749). Architectures for a peripheral businclude PCI, USB, and the like.

CPUs (1741), GPUs (1742), FPGAs (1743), and accelerators (1744) canexecute certain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(1745) or RAM (1746). Transitional data can be also be stored in RAM(1746), whereas permanent data can be stored for example, in theinternal mass storage (1747). Fast storage and retrieve to any of thememory devices can be enabled through the use of cache memory, that canbe closely associated with one or more CPU (1741), GPU (1742), massstorage (1747), ROM (1745), RAM (1746), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (1700), and specifically the core (1740) can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (1740) that are of non-transitorynature, such as core-internal mass storage (1747) or ROM (1745). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (1740). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(1740) and specifically the processors therein (including CPU, GPU,FPGA, and the like) to execute particular processes or particular partsof particular processes described herein, including defining datastructures stored in RAM (1746) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example;accelerator (1744)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (IC) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

APPENDIX A: ACRONYMS

-   JEM: joint exploration model-   VVC: versatile video coding-   BMS: benchmark set-   MV: Motion Vector-   HEVC: High Efficiency Video Coding-   SEI: Supplementary Enhancement Information-   VUI: Video Usability Information-   GOPs: Groups of Pictures-   TUs: Transform Units,-   PUs: Prediction Units-   CTUs: Coding Tree Units-   CTBs: Coding Tree Blocks-   PBs: Prediction Blocks-   HRD: Hypothetical Reference Decoder-   SNR: Signal Noise Ratio-   CPUs: Central Processing Units-   GPUs: Graphics Processing Units-   CRT: Cathode Ray Tube-   LCD: Liquid-Crystal Display-   OLED: Organic Light-Emitting Diode-   CD: Compact Disc-   DVD: Digital Video Disc-   ROM: Read-Only Memory-   RAM: Random Access Memory-   ASIC: Application-Specific Integrated Circuit-   PLD: Programmable Logic Device-   LAN: Local Area Network-   GSM: Global System for Mobile communications-   LTE: Long-Term Evolution-   CANBus: Controller Area Network Bus-   USB: Universal Serial Bus-   PCI: Peripheral Component Interconnect-   FPGA: Field Programmable Gate Areas-   SSD: solid-state drive-   IC: Integrated Circuit-   CU: Coding Unit

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

What is claimed is:
 1. A method for video encoding, comprising:receiving samples of a current block in a current picture; encoding, byprocessing circuitry of an encoding apparatus, the samples of thecurrent block according to a matrix based intra prediction to obtainencoded data, the encoding the samples of the current block including:determining entries of a vector based on neighboring samples of thecurrent block, each entry of the entries being determined based oncorresponding one or more of the neighboring samples of the currentblock, the entries of the vector being in an internal bit form having aninternal bit depth greater than a threshold bit depth for using a firstmultiplication tool implemented in the encoding apparatus that processesfewer bits than a second multiplication tool implemented in the encodingapparatus; converting the entries of the vector into a reduced bit formhaving a reduced bit depth satisfying the threshold bit depth for usingthe first multiplication tool implemented in the encoding apparatus;multiplying, using the first multiplication tool, the entries of thevector in the reduced bit form with entries of a matrix to calculate asubset of prediction samples of the current block; determining otherones of the prediction samples of the current block based on the subsetof the prediction samples of the current block; and encoding the samplesof the current block according to the prediction samples of the currentblock; and generating a coded video bitstream, the coded video bitstreamincluding the encoded data and prediction information indicative of thematrix based intra prediction for the current block.
 2. The method ofclaim 1, wherein the converting the entries of the vector into thereduced bit form comprises at least one of: right shifting a particularentry of the entries by one or more bits; and clipping the particularentry to a range corresponding to fewer bits.
 3. The method of claim 1,wherein the converting the entries of the vector into the reduced bitform comprises right shifting the entries of the vector by a number ofbits, and the method further comprises modifying, based on the number ofbits, a weight shifting variable that is used for aligningmultiplication results.
 4. The method of claim 3, further comprising atleast one of: determining the number of bits to shift based on theinternal bit depth; determining the number of bits to shift based on asignal in a high level syntax; and determining the number of bits toshift based on a look-up table.
 5. The method of claim 3, furthercomprising: decoding a look-up table from a high level syntax; anddetermining the number of bits from the look-up table indexed by theinternal bit depth.
 6. The method of claim 1, further comprising: usinga filtering tool to determine the entries of the vector based on theneighboring samples of the current block, the filtering tool being usedin a non-matrix based intra prediction.
 7. The method of claim 1,further comprising: selecting a subset of the neighboring samples of thecurrent block as the entries of the vector based on positions of theneighboring samples with reference to the current block.
 8. The methodof claim 1, further comprising: filtering first neighboring samples on afirst side of the current block to determine a first portion of theentries of the vector; and selecting a second portion of the entries ofthe vector from second neighboring samples on a second side of thecurrent block.
 9. The method of claim 1, wherein the other ones of theprediction samples of the current block are determined by applying alinear interpolation based on the subset of the prediction samples ofthe current block.
 10. An apparatus for video encoding, comprising:processing circuitry configured to: receive samples of a current blockin a current picture; encode the samples of the current block accordingto a matrix based intra prediction to obtain encoded data, the samplesof the current block are encoded by performing: determination of entriesof a vector based on neighboring samples of the current block, eachentry of the entries being determined based on corresponding one or moreof the neighboring samples of the current block, the entries of thevector being in an internal bit form having an internal bit depthgreater than a threshold bit depth for using a first multiplication toolimplemented in the apparatus that processes fewer bits than a secondmultiplication tool implemented in the apparatus; conversion of theentries of the vector into a reduced bit form having a reduced bit depthsatisfying the threshold bit depth for using the first multiplicationtool implemented in the apparatus; multiplication, using the firstmultiplication tool, of the entries of the vector in the reduced bitform and entries of a matrix to calculate a subset of prediction samplesof the current block; determination of other ones of the predictionsamples of the current block based on the subset of the predictionsamples of the current block; and encoding of the samples of the currentblock according to the prediction samples of the current block; andgenerate a coded video bitstream, the coded video bitstream includingthe encoded data and prediction information indicative of the matrixbased intra prediction for the current block.
 11. The apparatus of claim10, wherein the processing circuitry is configured to perform theconversion of the entries of the vector into the reduced bit form by atleast one of: right shifting a particular entry of the entries by one ormore bits; and clipping the particular entry to a range corresponding tofewer bits.
 12. The apparatus of claim 10, wherein the processingcircuitry is configured to: perform the conversion of the entries of thevector into the reduced bit form by right shifting the entries of thevector by a number of bits; and modify, based on the number of bits, aweight shifting variable that is used for aligning multiplicationresults.
 13. The apparatus of claim 12, wherein the processing circuitryis configured to determine the number of bits based on at least one of:the internal bit depth, a signal in a high level syntax, and a look-uptable.
 14. The apparatus of claim 10, wherein the processing circuitryis configured to: use a filtering tool to determine the entries of thevector based on the neighboring samples of the current block, thefiltering tool being used in a non-matrix based intra prediction. 15.The apparatus of claim 10, wherein the processing circuitry isconfigured to: select a subset of the neighboring samples of the currentblock as the entries of the vector based on positions of the neighboringsamples with reference to the current block.
 16. The apparatus of claim10, wherein the other ones of the prediction samples of the currentblock are determined by applying a linear interpolation based on thesubset of the prediction samples of the current block.
 17. Anon-transitory computer-readable medium storing instructions which whenexecuted by a computer cause the computer to perform: receiving samplesof a current block in a current picture; encoding the samples of thecurrent block according to a matrix based intra prediction to obtainencoded data, the encoding the samples of the current block including:determining entries of a vector based on neighboring samples of thecurrent block, each entry of the entries being determined based oncorresponding one or more of the neighboring samples of the currentblock, the entries of the vector being in an internal bit form having aninternal bit depth greater than a threshold bit depth for using a firstmultiplication tool implemented in the computer that processes fewerbits than a second multiplication tool implemented in the computer;converting the entries of the vector into a reduced bit form having areduced bit depth satisfying the threshold bit depth for using the firstmultiplication tool implemented in the computer; multiplying, using thefirst multiplication tool, the entries of the vector in the reduced bitform with entries of a matrix to calculate a subset of predictionsamples of the current block; determining other ones of the predictionsamples of the current block based on the subset of the predictionsamples of the current block; and encoding the samples of the currentblock according to the prediction samples of the current block; andgenerating a coded video bitstream, the coded video bitstream includingthe encoded data and prediction information indicative of the matrixbased intra prediction for the current block.
 18. The non-transitorycomputer-readable medium of claim 17, wherein the converting the entriesof the vector into the reduced bit form comprises at least one of: rightshifting a particular entry of the entries by one or more bits; andclipping the particular entry to a range corresponding to fewer bits.19. The non-transitory computer-readable medium of claim 17, wherein theconverting the entries of the vector into the reduced bit form comprisesright shifting the entries of the vector by a number of bits, and theinstructions which when executed by the computer cause the computer tofurther perform: modifying, based on the number of bits, a weightshifting variable that is used for aligning multiplication results. 20.The non-transitory computer-readable medium of claim 17, wherein theother ones of the prediction samples of the current block are determinedby applying a linear interpolation based on the subset of the predictionsamples of the current block.